Loose wheel nut indicator

A loose wheel nut indicator is a measuring tool that warns of loose wheel nuts, which is the most common cause of wheels on vehicles falling off.

Wheel nut indicators on a truck showing all nuts are as they were left.

Mechanical indicator
A single wheel nut indicator.

A common type of loose wheel nut indicators are small pointed tags, usually made of fluorescent orange or yellow plastic, which are fixed to the lug nuts of the wheels of large vehicles.[1] The tag rotates with the nut, and if the nut becomes loose, the point of the tag shifts noticeably out of alignment with the other tags. If too many lug nuts are loosened, the wheel can detach from the wheel stud; loose wheel nut indicators allow identification of loose nuts before this can occur.

Loose wheel nut indicators or lug nut indicators are used both by auto mechanics and drivers to identify lug nuts which require tightening, as well as by accident investigators to detect faults after accidents. Although generally not compulsory, road safety bodies frequently recommend their use,[2][3][4] especially on large or heavy vehicles such as buses, coaches, large vans, and trucks.[5]

An alternative to wheel nut indicators is to add a torque stripe. This is a small strip of polymer connecting the nut to the surface it is fastened to which breaks if the nut loosens.

Electronic sensor

Advancements in anti-lock braking systems (ABS) have made it possible to detect loose wheel nuts by using sensors from the ABS system in the car's software.[6] The system functions by detecting and recognizing vibrations which could indicate a loose wheel.

In 2018, Audi launched electronic wheel nut indicators on some of their more expensive models,[7] and by 2021 Audi had sold over 1 million cars with the technology.[8]

See also

References
  1. "What are the yellow plastic indicators on truck and bus wheels".
  2. "Highways Agency UK, Vehicle Wheel Nut Indicators" (PDF).
  3. "Transport for New South Wales, Safety Technologies for Heavy Vehicles and Combinations, P.11" (PDF).
  4. "NZ Transport Agency, Wheel Loss Information Sheet, P.2" (PDF).
  5. "Wheel Loss". Brake. Archived from the original on August 10, 2007. Retrieved 2007-08-19.
  6. Loose Wheel Indicator « NIRA Dynamics AB
  7. Loose Wheel Indicator selected by Audi for a range of car models
  8. Loose Wheel Indicator reaches 1 Million sold units and is ready for the next step
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